mysql

indexing on virtual column https://www.percona.com/blog/2016/03/07/json-document-fast-lookup-with-mysql-5-7/

Working With JSON Data In MySQL - Part 1 of 3 (basic usage) https://benjaminlistwon.com/blog/working-with-json-data-in-mysql-part-1-of-3/

psql

PostgreSQL JSON tutorial http://www.postgresqltutorial.com/postgresql-json/